This invention relates to an improvement of a spray device for spraying a mold releasing agent onto inner surfaces of mold halves of a die casting machine after taking out a molded product from the mold halves and blowing off chips remaining in the mold halves to clean the inner surfaces thereof.
A prior art die casting machine including a spray device is schematically shown in FIG. 1, in which a hydraulic or pneumatic cylinder-piston assembly 1 is secured to a stationary die plate 3 through a bracket 2 attached thereto. A spray head 4 provided with a plurality of spray guns 6 each having a cock is supported by the lower end of a piston rod 5 of the cylinder-piston assembly 1 so as to be vertically movable in accordance with the operation of the assembly 1. Movable and stationary mold halves 7 and 8 are supported by movable and stationary die plates 9 and 3, respectively.
In FIG. 1, the spray guns 6 eject a mold releasing agent such as Chem-Trend (Trade Mark, Chem-Trend Corp., U.S.A.) for preventing seizure of molten metal injected into the die mold halves. After the mold releasing agent has been sprayed, the spray head 4 is raised by the operation of the cylinder-piston assembly 1 and the movable die plate 9 is then slidably moved so as to engage the movable mold half 7 with the stationary mold half 8.
With the arrangement of the die casting machine of the type described above, the spray device of the die casting machine has to be moved to a position where the spray head 4 does not hinder the operation for exchanging the molds every time when the movable and stationary molds are exchanged with other ones. Although it is possible to change areas of the inner surfaces of the molds to be sprayed with the mold releasing agent by properly opening or closing respective cocks of the spray guns 6 in accordance with the dimensions of the molds exchanged, it is required to increase the stroke of the piston rod 5 in conformity with the dimensions of the molds. It is important to spray the mold releasing agent in a quantity which is sufficient, but, not excessive, over the entire surfaces of the molds. However, in an actual injection molding work, since various molds having different dimensions are used, a spray head with a number of spray guns must be used in order to satisfactorily spray the mold releasing agent onto the inner surfaces of the molds. This fact increases the number of spray guns 6, and elongates the piston stroke of the cylinder-piston assembly 1. Moreover, mist of the sprayed mold releasing agent is often generated when the mold releasing agent is sprayed from a large number of spray guns, and the spray guns 6 are choked by adhesion of splashed mold releasing agent. For the reason described above, troublesome maintenance of the spray guns should be made periodically, which results in additional work for an operator. Furthermore, after one spraying process, the spray head 4 is raised directly upwardly and the movable mold half 7 is moved to engage the stationary mold half 8. At this time, die molds or a molded product are often spoiled by "after-dribble" of the mold releasing agent from the spray guns 6 positioned directly above the molds. The drops or after-dribble of the mold releasing agent damage the appearance and quality of the molded product.